1. Field of the Invention
This invention relates to a method of estimating the need of capacity for different parts of a cellular radio system divided into location areas, mobile stations being arranged to send location update messages to the other parts of the system in predetermined situations. The invention relates further to a cellular radio system comprising a mobile telephone exchange, base stations and mobile stations, the geographical area covered by the cellular radio system being divided into location areas and the mobile stations being arranged to send location update messages by radio to the base stations in predetermined situations.
This invention relates to determining so-called Hot-Spot locations in a cellular radio system, which means finding possible bottlenecks as to the required traffic capacity. A problem associated with planning cellular radio systems consists in estimating the traffic capacity needed. Cellular radio systems are generally dimensioned by assuming that all mobile stations belonging to the system do not communicate simultaneously, but the aim of the dimensioning is to find the maximum conceivable number of telephones which are assumed to communicate in practice at a predetermined moment, after which the system is dimensioned in such a way that it is capable of coping with this load. In order that the dimensioning of the system at least to some extent may be based on reality (and not only on guesswork) within a predetermined geographical area, it is necessary to find out the number of mobile stations simultaneously located within said area.
2. Description of Related Art
Solutions for finding out the number of mobile stations located in a predetermined area are previously known, whereby the number of mobile stations is found out on the basis of measurement reports of active mobile stations (call going on). This means that, in a GSM (Global System for Mobile communications) system, for instance, active mobile stations measure continuously, while being on a traffic channel, besides the signal strengths of their own base stations, also signals from six strongest neighbouring base stations and transmit reports on measurement results continuously to the other parts of the system. However, the most significant drawback of this known solution is that it is based expressly on detecting active mobile stations. This means in practice that only those mobile stations through which a call is going on at said moment are taken into consideration. It is clear that this way of detection may give a rather distorted picture of the number of mobile stations actually located in the area, because passive phones located in the area, meaning those mobile stations through which no call is going on at said moment, are not considered in any way. However, the number of passive phones may be rather big, for which reason they should absolutely be taken into consideration when the system is dimensioned.
An object of this invention is to solve the above problem and to facilitate the dimensioning of the cellular radio system in such a way that the real number of phones located in a predetermined geographical area could be taken into consideration at the dimensioning better than before. This object is achieved by the method according to the invention, which is characterized in that for an estimation of the need of capacity in a predetermined geographical area: a new location area covering said area is defined for the system; said new location area is defined to be the location area of the base stations located in said area, at least during the time of estimating the need of capacity; location update messages transmitted from the new location area are monitored; statistics are kept on the location update messages detected, those statistics including an information on at least the number of location update messages received from the area; and the need of capacity for the area is estimated on the basis of the data stored in said statistics.
The invention is based on the idea that the number of mobile stations located in a predetermined area can be estimated more accurately than before by compiling statistics on location update requests/messages transmitted from the mobile stations to the other parts of the system, said requests being transmitted by the mobile stations in a manner known per se to the other parts of the system in predetermined situations anyway, for instance when they move from a location area to another or at predetermined intervals. When a new location area is initially created for the area to be monitored, the size (surface area) of which new area can be considerably smaller (for instance a single radio cell or a few of them) than the location areas used normally, the need of capacity can be ascertained accurately within the very area which is of interest. When statistics are kept on location update messages during a relatively long period, the number of phones in the area can be found out more accurately than before, because the number of passive mobile stations can be detected as well. The most significant advantage of the method of the invention is thus that it gives a more accurate picture of the number of phones located in the predetermined geographical area of interest, whereby potential bottlenecks concerning the capacity of the system can be found more easily than previously, and that the method of the invention can be applied by very small measures to existing systems by means of a software.
In a preferred embodiment of the method of the invention, a radio cell-specific information is maintained on from which location area mobile stations are coming when they send location update messages to a predetermined radio cell. This embodiment of the invention enables that statistics can be kept on the movements of the mobile stations. Accordingly, in the vicinity of harbours, airports and frontier crossing points, for instance, it is possible to keep statistics on where the mobile stations xe2x80x9cturning upxe2x80x9d come from.
In a second preferred embodiment of the method of the invention, a message is initially sent to the mobile stations belonging to the system, the message making the mobile stations shorten that cyclic time period during which they at least once send a location update message to the other parts of the system. By means of this preferred embodiment of the invention, it is possible to make sure in advance that a location update message is received during a relatively short monitoring period from as many mobile stations as possible.
In a third preferred embodiment of the method of the invention, an information on the number of those mobile stations located in the area from which a connection, such as a call, is going on at a predetermined moment is also entered into the statistics. This embodiment enables a more accurate estimation of the need of capacity than before, because an information on the number of both passive (no call going on) and active (a call going on) mobile stations can then be entered into the same statistics.
Another object of the invention is a cellular radio system to which the method of the invention can be applied. The cellular radio system of the invention is characterized in that the system comprises storing means arranged in a base station controller for monitoring location update messages received by base stations and for storing data contained in the location update messages in a memory means in response to detecting a location update message, and means for transmitting the data stored in the memory means further to an operator of the system for an estimation of the need of capacity for the different parts of the system on the basis of the data stored in the memory means.
According to the invention, it is preferable to monitor location update messages expressly in a base station controller, via which location update messages are transmitted anyway. Accordingly, applying the invention does not require any additional new components in the system, but the invention can also be applied to existing systems by reprogramming the base station controllers. This enables an estimation of the need of capacity without significant additional costs.
The preferred embodiments of the method and the cellular radio system of the invention appear from the attached dependent claims 2 to 4 and 5 to 7.